Andy Murray booked his place in the Cincinnati Masters final with a commanding win over big-serving Croatian Ivo Karlovic.

The British No 1 beat his experienced opponent 6-4 6-4 and will now face a showdown against the ever-impressive Rafael Nadal or Novak Djokovic.

Karlovic, 29, was the man responsible for Roger Federer's premature exit earlier in the tournament but had no answer for the 21-year-old Scot - who played with verve and confidence despite the oppressive temperature.

Murray, who has never won a Masters title, started confidently against Karlovic's formidable service game but proceeded to lose on his own serve in the second game of the match.

He immediately broke back, allowing his opponent no time to consolidate his lead before stringing together some fine points on his way to a second consecutive break and a 4-3 lead.

The pair then traded games before Murray, who came into the match having beaten Karlovic on two previous occasions, served out for the opening set.

The British No 1's return game was growing in stature by the minute and he put his 6ft 10in rival through the wringer with a series of break points in the opening game of the second set.

Karlovic manfully saved a handful of them before finally handing Murray the game with a misjudged volley.

Murray did not initially take advantage and allowed Karlovic to move back level with a break of his own before eventually triumphing for the fourth time against serve.

That put the Dunblane native 5-4 up with the chance to serve for victory.

He did so with some panache, losing just one point on the way, and will now be facing up to the prospect of what is sure to be a sterner test in the final against world No 1-elect Nadal or Djokovic.

"I felt like I was hitting the ball great today," said the Scot. "I see his serve pretty well and it comes through to me at quite a nice height. He likes the quick points, but when you can make a lot of returns it disrupts him."

o Tommy Haas, Sam Querrey, Donald Young, Ashley Harkleroad and Alexandra Stevenson are among those entered in today's inaugural Shotgun 21 World Championships, a tennis competition in which men and women play against each other.

The one-day tournament in Pacific Palisades offers a purse of more than $20,000 (£10,000) in prize money, with $10,000 and a limited edition Fender Stratocaster going to the winner.

Tournament founder/director Steve Bellamy said the event will have a 32-player main draw, and should be completed in about three hours. He said a committee examined the value and qualifications of every entrant and choose the top 28.

The other four will come from a qualifier earlier in the day that's open to the public.

There are four significant rule changes from traditional tennis: no overhand serve, second serves or lets, and the winner is the first to reach 21 points as opposed to deuce/ad scoring. All serving is drop-hit and struck from below the waist.

"The player field for this event is flat-out amazing," Bellamy said. "Even the celebrities playing are incredible."

They include Gavin Rossdale, the founder and lead singer of the band "Bush," and husband of entertainer Gwen Stefani; actor/model Boris Kodjoe, and actress/model Sara Foster, Haas's girlfriend.

Haas, ranked as high as No. 2 in the world, lost to Wimbledon champion Rafael Nadal 6-4, 7-6 on Thursday night in the Cincinnati Masters.

Querrey is the third-ranked male in the US; Harkleroad is the fifth-ranked woman, and Stevenson is in the midst of a comeback after a shoulder injury. She reached the Wimbledon semi-finals as an 18-year-old in 1999.